Coil structure for electric watches

ABSTRACT

A coil structure for an electric watch having a balance wheel formed with a pair of spaced discs on which are mounted two pairs of permanent magnets aligned in facing relation on said discs. Detecting and driving coils are wound coaxially and mounted separate from said balance wheel in the gap between said permanent magnets. The detecting and driving coils are mounted so that, at the center of oscillation of the balance wheel, most of the magnetic flux is interlinked with a respective side of the driving coil.

United States Patent 1191 Tsuruishi et a1.

COIL STRUCTURE FOR ELECTRIC WATCHES Inventors: Yuki Tsuruishi; OkitoNaito;

Masanao Matsuzawa, all of Suwa, Japan Assignee: Kabushiki Kaisha SuwaSeikosha,

Tokyo, Japan Filed: Feb. 27, 1973 Appl. No.: 336,298

Related U.S. Application Data Continuation-impart of Ser. No. 127,893,March 25, 1971, abandoned.

Foreign Application Priority Data Mar. 31, 1970 Japan 45-26529 U.S. Cl58/28 A, 310/36, 318/132 lint. Cl .L G04c 3/04 Field of Search 58/28 R,28 A; 310/36;

[ Apr. 16, 1974 [561 References Cited UNITED STATES PATENTS 3,365,6351/1968 Shelley 318/128 3.s1s,s1s 6/1970 Reich 318/128 3,524,118 8/1970Reich 318/128 Primary Examiner-Lawrence R. Franklin Attorney, Agent, orFirm--Blum, Moscovitz, Friedman & Kaplan [5 7] ABSTRACT A coil structurefor an electric watch having a balance wheel formed with a pair ofspaced discs on which are mounted two pairs of permanent magnets alignedin facing relation on said discs. Detecting and driving coils are woundcoaxially and mounted separate from said balance wheel in the gapbetween said permanent magnets. The detecting and driving coils aremounted so that, at the center of oscillation of the balance wheel, mostof the magnetic flux is interlinked with a respective side of thedriving coil.

2 Claims, 12 Drawing Figures PATENTEDAPR 1 6 1974 SHEET 0F Q COILSTRUCTURE FOR ELECTRIC WATCHES This is a continuation-in-part of ourco-pending application Ser. No. 127,893 filed Mar. 25, 1971 nowabandoned.

BACKGROUND OF THE INVENTION The present invention relates to a coil formof electric watch with permanent magnets mounted on the balance wheel.The object of this invention is to improve the coil of such electricwatches with permanent magnets mounted on the balance wheel and toprovide a low-priced electric watch. In an electric watch with permanentmagnets mounted on the balance wheel, wherein the balance wheel isprovided with permanent magnets and driven by a coil mounted outsidethereof, the magnetic flux density of the permanent magnet is increasedand turns on the coil are increased in order to obtain a wide amplitudeof oscillation of the balance wheel through a small consumption current.

In such prior art arrangements, a highly effective magnetic materialsuch as platinum cobalt was used as a permanent magnet and a very thinwire was wound closely on the coil in order to make the parts smallerabout the balance. Such permanent magnets and coil wire were of highcost, while the making and handling of the coil at assembly proveddifficult.

In order to eliminate the above disadvantages, it was proposed that whena low-priced permanent magnet is used, the shape of magnet should belarge in order to obtain the necessary magnetic flux density or a verythin wire should be wound closely on the coil in order that the watchcan be operated even if the magnetic flux density is small. However,neither of these alternatives are desirable for the efficiency of thewatch and the production thereof.

SUMMARY OF THE INVENTION Generally speaking, in accordance with theinvention, an electric watch is provided having an oscillating balancewheel carrying two pairs of permanent magnets defining a magneticcircuit having air gaps between facing permanent magnets of oppositepolarity. Fixed detecting and driving coils are provided wound coaxiallyand mounted in the gaps between the permanent magnets. The detecting anddriving coils'are positioned so that, at the center of oscillation ofthe balance wheel, most of the magnetic flux of the field passingthrough each pair of the permanent magnets is inter linked with arespective side of the driving coil, and so that, at said center ofoscillation, the magnetic flux interlinked with the detecting coil issubstantially smaller than that interlinked with the driving coil.Driving circuit means is provided including the driving and detectingcoils, the driving circuit means being adapted to apply driving pulsesto the driving coils in response to each pulse induced in the detectingcoil of a selected polarity. I

The object of this invention is to provide magnet and coil of compactsize which would permit a low manufacturing cost by eliminating theabove disadvantages, i.e. to provide a method which increases drivingefficiency ofa coil wound with thick wire and having a relatively smallnumber of turns. it is thus possible to obtain a highly efficientelectric watch using a low-priced magnet and coil.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is had to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a front view of a balance wheel and the coils of theconventional type of electric watch with permanent magnets mounted onthe balance wheel;

FIG. 2 is a plane view of the balance wheel and the coils of FIG. 1:

FIG. 3 shows one embodiment of a driving circuit of the conventionaltype of electric watch with permanent magnets mounted on the balancewheel;

FIG. 4 shows voltage wave forms at three points in the driving circuitof the conventional type of electric watch with permanent magnetsmounted on the balance wheel shown in FIG. 3;

FIG. 5 is a front view of the balance wheel and the coils of theelectric watch with permanent magnets mounted on the balance wheelaccording to the invention;

FIG. 6 shows one embodiment of the coil according to the invention;

FIG. 7 shows voltage wave forms at said three points in said drivingcircuit of the electric watch with permanent magnets mounted on thebalance wheel according to the invention;

FIG. 8 is a top plan view of the balance wheel and coils of FIG. 5;

FIGS. 9(a), 9(b) and 9(c) are schematic front views of the balance wheeland coils in accordance with the invention depicted respectively atthree relative positions; and

FIG. 10 shows wave forms of the voltage induced in the detecting anddriving coils respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is made to thedrawings wherein FIG. I is a front view of the balance wheelof aconventional type of electric watch with permanent magnets mounted onthe balance wheel provided with two discs, and wherein Z is a balancestaff and 3, 4i, 5 and 6 are permanent magnets. Permanent magnets 3 and5 are disposed in alignment with and facing permanent magnets 4 and 6respectively. 7 is a phase detecting coil and 8 is the driving coil.

FIG. 2 is a plan view of FIG. 1 wherein 9 is a winding frame, 10 and1111 are balancing weights for balancing the balance wheel, 12corresponds to the permanent magnets 3 and 4, 13 corresponds to thepermanent magnets 5 and 6, and M is a coil.

In FIG. l, the coil is formed with a detecting coil 7 and a driving coil3. The detecting coil and the driving coil can be formed as a unit bywinding the two coils together.

FIG. 3 shows one embodiment of the driving circuit of the electric watchwith permanent magnets mounted on the balance wheel. In FIG. 3, 15 is adetecting coil, 16 a condenser for cutting off the direct current. 17 abase bias resistance, W the driving coil, 19 a driving transistor and 20a voltage source of direct current.

FIG. 4 shows voltage wave forms at points A, B, C of said drivingcircuit when driving the balance wheel of FIG. 1. A wave form of thevoltage induced in the detecting coil 15 is shown by a broken line inFIG. 4(A). The wave form at operating times falls down in a range wherethe driving transistor is conducting as shown by the wave form in solidline, due to the addition of the voltage drop of internal resistancecaused by the electric current flowing in detecting coil 15. An inducedvoltage having a phase opposite to that of detecting coil 15 occurs onthe collector side of driving coil 18 as shown in FIG. 4. When the basevoltage B rises above the base conducting level of the drivingtransistor, the electric current flows in the base through detectingcoil 15 and the collector voltage C of the driving transistor goesdown'to the conductive level.

At this moment, the condenser 16 for cutting off the direct current ischarged by the current flowing from the detecting coil to the base. Thecharging voltage is used as a base bias voltage for keeping the drivingtransistor in cut off condition when the driving transistor is cut off.This is apparent from FIG. 4(B). The peak value of the positive side ofthe detecting voltage caused by oscillation of the balance wheel is notthe same where the balance wheel moves clockwise or counterclockwise.The same is true in the case of the current flowing in the base.

Therefore, the difference in the base bias voltage between immediatelybefore a single driving pulse occurs and a double driving pulse occursis V If the base bias resistance is too small, the driving transistorenters into the conducting area before the single driving pulse occurs,and unnecessary current consumption is increased. If the base biasresistance is too large, the negative base bias voltage is increased andthe width of the driving pulse and the amplitude are reduced. The basebias resistance must fall within a proper range of values for securingthe operation of the balance wheel and it is necessary that the doubledetecting voltage be large enough in the above range of values.

Because the negative bias voltage, which occurs immediately before thedouble detecting voltage, is much increased, the driving transistorcannot conduct perfectly unless enough detecting voltage is produced,the internal loss of the transistor is increased, and the amplitude ofthe balance wheel is reduced.

As is clear from above, turns on the detecting coil should be added inorder to obtain enough detecting voltage. llowever, turns on the drivingcoil should be reduced to contain the coil in a limited area. As aresult, the voltage induced in the driving coil is reduced, theincreased current consumption is not applied as energy for the balancewheel and the amplitude is reduced. In order to avoid abovedisadvantages, many more turns of very thin wire are added onconventional coil structures.

The object of this invention is to provide a method wherein turns on thedetecting coil are reduced. FIG. is a front view of the balance wheel ofone embodiment of an electric watch with magnets mounted on the balancewheel according to the invention. In FIG. 5, 21 is a driving coil and 22a detecting coil.

FIG. 6 is a plan view of the coils 21 and 22. 23 is an inner terminal,24 a connecting point between the driving coil 21 and the detecting coil22, 25 an outer terminal and 26 a coil frame.

FIG. 7 shows the voltage wave forms at three points in the circuit ofFIG. 3 when the wires of the detecting and driving coils are woundcoaxially. FIG. 7 corresponds to FIG. 4. If the wires of the coils arewound coaxially, the magnetic flux produced by pairs of magnets, 3, 4and 5, 6 does not pass through the detecting coil 22 at the same time,so the peak values on positive and negative sides of the induced voltagein the detecting coil 22 are the same as shown in FIG. 7. Base biasvoltage is almost the same immediately before the single and doubledriving pulses occur as shown in FIG. 7(3). The difference V, of FIG. 7is much smaller than V,,, in FIG. 4(B).

Therefore, even if the peak value of double detecting voltage is small,the driving transistor can be conductive as the negative base biasvoltage is reduced, and turns on the detecting coil 22 may be reduced.Thus, low-priced thick wire can be used. The phase of the drivingcurrent is a little shifted from a phase at which the driving currentgives maximum energy to the magnet, but actually this makes nodifference. In the coil according to this invention, the connectingpoint 24 is connected to an electric source, an advantageous arrangementfor disposing the terminals of coils.

Referring now to FIGS. 8 and 9, it is seen that balance wheel 1oscillates so that the permanent magnets pass driving coil 21 anddetecting coil 22. Double headed arrow 27 of FIG. 8 represents the locusof the path of the center portion of the permanent magnets. FIG. 10(a)depicts a voltage induced in the detecting coil 22 during each cycle ofoscillation, while FIG. 10(b) depicts the voltage induced in the drivingcoil during each such cycle.'Three points in the forward motion portionof the cycle are identified as 1,, t and I The relative position of thepermanent magnets and the driving and detecting coils at each of saidthree times are depicted respectively in FIGS. 9(a), 9(b) and 9(c). Timet;, represents the center of oscillation of the balance wheel, at whichpoint it is seen from FIG. 9(c) that most of the magnetic flux of thefield passing through each pair of the permanent magnets is interlinkedwith a respective side of the driving coil. Further, it is apparentthat, at said center of oscillation, the magnetic flux interlinked withthe detecting coil is substantially smaller than that interlinked withthe driving coil. In this matter, maximum driving force is applied tothe balance wheel at said center of oscillation, thereby insuringefficient and accurate driving of the balance wheel in both directionsof oscillation thereof.

As described above, according to the invention, turns on the detectingcoil of an electric watch with magnets mounted on the balance wheel canbe reduced and consequently, as turns on the driving coil can beincreased, the coil can be made by using a relatively thick wire. As aresult, a low-priced coil adapted for easy handling can be obtained.This structure is also very advantageous for mass scale production ofthis type of electric watch. Moreover, as the detecting voltage may besmall according to the invention, lower-priced magnets may be used.

It will thus be seen that the objects set forth above, and those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above constructions withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. An electric watch comprising an oscillating balance wheel having ashaft and a pair of spaced discs mounted on said shaft; two pairs ofpermanent magnets, one of each of said pairs of permanent magnets beingmounted on each of said discs in facing relation to the other of saidpermanent magnets, the permanent magnets of each of said pairs beingpolarized to produce a magnetic field in the gap therebetween extendingin a direction opposite to the field in the gap between the other ofsaid pairs of permanent magnets so as to form a closed magnetic circuit;a detecting coil; a driving coil, said detecting and driving coils beingseparate from said balance wheel and mounted in the gaps between saidpermanent magnets, said detecting coil being wound coaxially inside ofsaid driving coil, said detecting and driving coils being positioned sothat, at the center of oscillation of said balance wheel most of themagnetic flux of said field passing through each pair of said permanentmagnets is interlinked with a respective side of said driving coil, andso that, at said center of oscillation, the magnetic flux interlinkedwith said detecting coil is substantially smaller than that interlinkedwith said driving coil; and driving circuit means including said drivingand detecting coils, said driving circuit means being adapted to applydriving pulses to said driving coils in response to each pulse inducedin said detecting coil of a selected polarity.

2. An electric watch as recited in claim 2, wherein said driving circuitmeans includes transistor means having a base, emitter and collector; avoltage source, said driving coil and voltage source being connected inseries with the emitter-collector path of said transistor means; andbase circuit means including said detecting coil, capacitor meansconnected in series with said detecting coil and resistor meansconnected in parallel with said series connection of said detecting coiland capacitor means, the time constant of said capacitor means andresistor means being selected such that said transistor means is drivento conduction to apply a driving pulse to said driving coil in responseto each of said pulses induced in said detecting coil of aselectedpolarity.

1. An electric watch comprising an oscillating balance wheel having ashaft and a pair of spaced discs mounted on said shaft; two pairs ofpermanent magnets, one of each of said pairs of permanent magnets beingmounted on each of said discs in facing relation to the other of saidpermanent magnets, the permanent magnets of each of said pairs beingpolarized to produce a magnetic field in the gap therebetween extendingin a direction opposite to the field in the gap between the other ofsaid pairs of permanent magnets so as to form a closed magnetic circuit;a detecting coil; a driving coil, said detecting and driving coils beingseparate from said balance wheel and mounted in the gaps between saidpermanent magnets, said detecting coil being wound coaxially inside ofsaid driving coil, said detecting and driving coils being positioned sothat, at the center of oscillation of said balance wheel most of themagnetic flux of said field passing through each pair of said permanentmagnets is interlinked with a respective side of said driving coil, andso that, at said center of oscillation, the magnetic flux interlinkedwith said detecting coil is substantially smaller than that interlinkedwith said driving coil; and driving circuit means including said drivingand detecting coils, said driving circuit means being adapted to applydriving pulses to said driving coils in response to each pulse inducedin said detecting coil of a selected polarity.
 2. AN electric watch asrecited in claim 2, wherein said driving circuit means includestransistor means having a base, emitter and collector; a voltage source,said driving coil and voltage source being connected in series with theemitter-collector path of said transistor means; and base circuit meansincluding said detecting coil, capacitor means connected in series withsaid detecting coil and resistor means connected in parallel with saidseries connection of said detecting coil and capacitor means, the timeconstant of said capacitor means and resistor means being selected suchthat said transistor means is driven to conduction to apply a drivingpulse to said driving coil in response to each of said pulses induced insaid detecting coil of a selected polarity.